Preserving wood



Patented Feb. 27, 1934 PATENT OFFICE A 1,948,551 PRESERVING 'woon I Harold W. Walker, Hamilton, Ohio, assignor to Pennsylvania Lubricating Company, a corporation of Delaware No'Drawing. Application April 19, 1930 Serial No. 445,838

17 Claims.

This invention relates to preserving wood; and it comprises a method of permanently preserving wood against attack by living organisms, wherein wood is impregnated with a heavy oily medium carrying in solution diphenylamine and arsenic trichlorid; and it further comprises a new composition of matter suitable for impregnating wood containing arsenic trichlorid and diphenylamine; all as more fully hereinafter set forth and as claimed.

In preserving wood by the usual processes, the wood is impregnated with a heavy or viscous oil in various well known ways involving vacuum or pressure, or both in alternation, hot baths, etc. In

preserving ties, telephone poles, structural timbers, piles, etc., the preservative oil is usually a coal tar creosote although various petroleum oils of asphaltic nature have been proposed. Fuel oil is sometimes used either alone or in admixture 0 with a creosote or other heavy oil. Coal tar "creosote is composed of neutral oils for the most part and is not particularly phenolic. In the wood most of these oily impregnants act merely as mechanical protection or shield for the wood fibers; they have some preservative value but very little toxic effect upon insects or fungi. Mostly they tend to be washed out of the wood in time.

Many propositions have been made in the prior art to improve impregnating oils by the addition of various substances having a positive fungicidal or insecticidal value or both. Copper salts, mercury salts, arsenicals and a variety of other materials have been proposed. The difficulty with most of these preparations is that they do not actually poison the-fibers of the wood; and this is what is necessary. Insofar as the toxic remains in'solution in the oil, it adds nothing to the protection; insofar as it is filtered out by the fiber, it can give only local protection. It is found in 4 practice that with most of these toxics, protection of the wood does not endure much beyond the time when the oil begins to disappear. Among the best of these additionsis a particular arsenical preparation diphenylaminechlorarsine, usually called D. M. Probably because of its assuming some particular relation to the fiber and because of its slight solubility in water this poison is particularly eflfective in giving lasting protection against borers and insects of various kinds.

5 It is quite effective even when used in small concentrations in the impregnating oil and there is a persistence of its poisoning effect in the wood irrespective of movements of the oily carrier; that is, if some of the impregnatingoil leaves the wood or leaches out in time, the poisonous properties of the wood as regards insects and other organ isms do not lessen substantially whether the wood remain in the air or under water. In other words, while oil takes D, M. into the wood, removal of the oil does not take out the D. M. 1

An objection to the use of diphenylaminechlorarsine, however, is that it is an expensivechemical; the manufacture being laborious and dangerous and requiring special apparatus. The commercialmaterial, like all concentrated arsenicals, is dangerous to handle. It dissolves slowly in oils of the class here useful, its solubility being quite small. In oils it forms more of a dispersion than a solution. It is diiiicult to secure uniform distribution of ready made D. M. in a large body of oil and to carry it into and uniformly through wood. It is filtered out in part. Without uniform distribution, there is no guarantee of a uniform and lasting poisoning of the wood.

I have found that I can obviate the noted dis- 7 advantages and secure certain new advantages by using in lieu of diphenylaminechlorarsine a direct solution of diphenylamine and arsenic trichlorid in the oil. Both are readily dispersed or dissolved in oil. In the case of diphenylamine 3 no danger attaches to handling it and in the case of arsenic trichlorid, the liquid from the drums can be directly piped into the oil or into a fraction of it. No risk to the operator is necessary and there is no delay awaiting solution as in the case of D. M. When dissolved in the oil the materials used probably react in time to form diphenylaminechlorarsine. Formation of this product may take place in the oil, before or after impregnation of the wood, and to a considerable extent during impregnation, particularly when heat and pressure are applied. Insofar as formation takes place in or on the fiber, this is distinctly advantageous. Formation of diphenylaminechlorarsine in situ, either in the impregnating medium and uniformly distributed therein or in the wood, is one of the objects of my invention.

In preparing a preservative impregnant for wood, I have found, as stated in a prior and 00- 109 pending application Serial No. 228,107, filed October 22, 1927, that the properties of toxicity, uniformity of impregnation and persistence of the preservative action are increased and improved by incorporating in the impregnant ingredients 10 of three different types, exemplified respectively by montan wax, fuel oil, and an arsenical organic compound. Free liquidity of the protective oil is of no advantage except during impregnation; and is afterwards disadvantageous as has- 110 tening the time when the oil leaves the wood, either by washing out by water or by capillarity. By dissolving montan wax in fuel oil, the oil is converted into a fusible solid or semi-solid, quite as readily incorporated into the wood when hot and far more fixed in position after cooling. Compositions containing ingredients of these three types in proper proportions are preservative impregnants for wood and the like which are readily and uniformly taken up, are not leached out to an appreciable extent by solution or emulsification in water, are not dislodged by water or thermal expansion and contraction, and do not attack the wood itself. They are, in short, permanent preservatives. Instead of montan wax, I can use any other substance which is a solid or plastic under ordinary atmospheric conditions and which is soluble in or miscible with the particular oil used. The mixture of the two is usually, but not necessarily, a solid at ordinary temperatures.

It is diflicult to thicken an oil containing D. M. by adding waxes, etc., and secure a homogeneous preparation. In dissolving arsenic trichlorid. and diphenylamine in the oil this lack of homogeneity does not occur.

As a vehicle I may use any of the preservative oils and other liquids commonly used for impregnating wood. Both creosote and fuel oil are good vehicles and either of them may be used along or they may be mixed. Creosote has a certain preservative value and fuel oil prevents checking of the wood. As fixer, montan wax may be replaced in whole or in part by ceresine wax, ozokerite, laterite, mineral rubber, parafiin and the like, or by mixtures of them. Naphthalene or sulfur, or both, may be added. Usually the fixer is melted and then mixed with the liquid vehicle to which the toxic is added. In some cases the mixture of vehicle and fixer is a simple solution. When the finished impregnant is a solid or plastic with a melting point above atmospheric temperature, impregnation is effected with the impregnant molten.

In the present invention the impregnating material may be that of said prior application with the exception that instead of using a previously made organic arsenical preparation, I use conjointly diphenylamine and arsenic trichlorid added either to the wax or to the oil. For many purposes, however, an effective and persistent preservative toxic impregnant is made without wax, diphenylamine first and thenarsenic trichlorid being simply added to a heavy oil, such for example as a topped crude petroleum or a heavy petroleum residual oil of either asphaltum or paramn base.

I have found that excellent fixed preservatives result from dissolving naphthalene in warm petroleum oil. Suitable proportions are 3 parts of naphthalene by weight to 2 parts of heavy oil. This mixture is solid under normal atmospheric conditions. In place of naphthalene I may use beta-naphthol or anthracene. To such a combination of vehicle and fixer it is usually advantageous to add a toxic and I have found that small quantities of diphenylamine and arsenic trichlorid impart to the impregnant the desired toxic property in high degree.

While it is advantageous to mix the diphenylamine and the AsCls in the impregnating fluid in about equimolecular proportions, no harm is done by a slight excess either way. The operation does not require skilled supervision. Where it is desirable, relatively large amounts of the two chemicals can be used, seeming more effective poisoning of the wood than can be effected by the amounts of D. M. which can be dissolved in oils.

For most purposes the addition of arsenic trichlorid and of diphenylamine to an impregnating fluid is usually less than 5 per cent in sum of the two substances together, reckoned on theweight of the fluid. Sometimes an addition of as little as 0.1 per cent is sufliciently effective, but in general the effectiveness increases with the amount of addition up to 5 per cent. Addition of the two reagents beyond 5 per cent is possible but usually the expense outweighs the advantage.

Impregnation of the wood by the above described toxic impregnants is accomplished by usual and well known methods. When the impregnant is a solid it is melted. Simple soaking of the wood in the liquid toxic preservative is often all that is required. The vacuum and pressure process, however, gives a better impregnation. In one such process green or seasoned wood in the form in which it is to be used is put into iron cylinders provided with steam coils. On each cylinder a vacuum of 28 inches of mercury is drawn and maintained for three hours. The cylinder is then filled with the impregnant which has been previously heated and to which has been made the addition of diphenylamine followed by that of arsenic trichlorid. Then a pressure of 100 to 200 pounds per square inch is applied by a pump and maintained along with a moderately high temperature for three hours. Or the required pressure may be established and maintained by heating the impregnant in a closed container by means of steam pipes. With thorough impregnation dry wood may take up as much as 40 per cent of its weight of impregnant or around 30 pounds per cubic foot of wood. For preserving seasoned railroad ties good re sults are obtained in using an impregnant composed of topped crude petroleum of 28 to 32 as. gravity containing added diphenylamine and ar senic trichlorid. The oil may be used with or without an addition of naphthalene or the like. To this oil the two reagents are added in proportions of from 1 to 2 pounds of each reagent per barrel (42 gallons) of oil. If desired, montan wax or a paraflin fixer in a quantity of about one-third to one-half that of the oil can be melted and stirred into the oil after the addition of the two chemicals. The ties are impregnated by a vacuum-pressure-temperature process, using pressures between 100 and 200 pounds per square inch with a temperature around to C. When using impregnants which are solids at ordinary temperatures, the wood and the impregnants are allowed to cool in the impregnating chamber to a temperature somewhat higher than the solidification point, then the molten impregnant is drawn off in a liquid state and the ties are removed from the chamber. After subsequent cooling in the air the ties are ready for use.

Wood treated with the toxic impregnant prepared as herein described has been found by test to be lastingly immune from rot and from attack by insects and organisms such as the borers destructive of Wood.

What I claim is: y

1. The method of preserving wood which comprises admixing diphenylamine and arsenic trichlorid with an organic oil and impregnating wood with the mixture.

2. The process of preparing a wood preservative which comprises adding diphenylamine and arsenic trichlorid to an impregnating medium lltl selected from a group consisting of oils and creosote.

3. The process of preparing a wood preservative which comprises adding arsenic trichlorid and diphenylamine to an organic oil and further adding to said oil a miscible thickening body having the properties of a fixer.

4. The process of preparing a wood preservative which comprises adding arsenic trichlorid and diphenylamine to a heavy petroleum oil and mixingwith said oil a quantity of montan wax.

5. The process of preparing a wood preservative which comprises adding to an impregnating oil between 0.1 and 5 per cent of its weight of diphenylamine and arsenic trichlorid in substantially equal molecular proportions.

'6. The process which comprises impregnating "W00d with a heavy petroleum oil to which diphenylamine and arsenic trichlorid in substantially equal molecular proportions have been added.

7. The process which comprises impregnating wood under heat and pressure with an oily medium to which diphenylamine and arsenic trichlorid in substantially equal molecular propor-' tions have been added.

8. The process which comprises impregnating wood with an oily medium in which diphenylamine and arsenic trichlorid have been dissolved.

9. As a new composition of matter suitable for impregnating and preserving wood, an oily vehicle containing arsenic trichlorid and also containing diphenylamine.

for impregnating and preserving wood, a mixture of liquid oil and a thickening body miscible therewith, said mixture containing arsenic trichlorid and also containing diphenylamine.

11. As a new composition of matter suitable for impregnating and preserving wood, a mixture of liquid oil and a thickening body dissolved therein, said mixture containing arsenic trichlorid and also containing diphenylamine.

12. As a new composition of matter suitable for impregnating and preserving wood, a mixture of petroleum oil and naphthalene, said mixture containing arsenic trichlorid and also containing diphenylamine.

13. The process of making a composition for preserving wood whichwcomprises dissolving arsenic trichlorid and diphenylamine in a petroleum oil and allowing slow reaction to take place between the dissolved bodies.

14. ,The process of preserving wood which comprises impregnating wood with the solution of claim 13 prior to completion of reaction between the arsenic trichlorid and the diphenylamine.

15. The process of claim 8 wherein impregna-.

tion of the wood is by a vacuum-pressure-temperature process.

16. The process of claim 8 wherein the diphenylamine and arsenic trichlorid are present in the said oily medium in proportions up to 5 per cent by weight.

17. The process of claim 8 wherein the said oily medium contains a miscible thickening body having the properties of a fixer.

HAROLD W. WALKER. 

